Typically, when your dog has to have surgery, the vet tech is the one who is responsible for shaving the area to be operated on. The area to be shaved is based on what type of surgery your pooch is about to undergo. For example, if your pup is being spayed, her abdomen will be shaved from the sternum all the way to the groin. The area is shaved to create a sterile operating field that is free of hair and other debris. Of course, you can also take care of shaving your pup before you take him in for his surgery (though the tech will still go over the area again).
Your dog is probably just as happy about being shaved as he is about undergoing surgery. He probably doesn't have much of an idea what is going on. But, if it makes you feel better, there is no reason why you shouldn’t be the one to handle the preliminary shaving.
Although it would be unusual for a pet owner to shave their dog prior to surgery, there may be times when it is necessary. The most important thing to remember is that you need to shave all signs of hair from the area to be operated on. Chances are good the veterinary surgeon or his assistants will still go over the area one more time before the surgery.